1. Field of the Invention
The present invention relates to an electroluminescent panel and a method of manufacturing the electroluminescent panel.
2. Description of the Related Art
An organic electroluminescent panel (hereinafter referred to as “organic EL panel”) is a display panel featuring higher visibility than a liquid crystal panel because of its self-luminescence and thinness and light weight because of the absence of backlight. It is a focus of attention as a display panel to replace the liquid crystal panel in the near future. Generally, an organic electroluminescent element (hereinafter referred to as “organic EL element”) used in the organic EL panel emits light when electrons injected from an electron injecting electrode to an electron transport layer are recombined with holes injected from a hole-injecting electrode to a hole transport layer at the interface between the luminescent layer and the hole transport layer or within the luminescent layer near the interface. Organic EL elements to display colors are manufactured by forming an organic luminescent layer by vapor deposition of organic material capable of emitting red, green and blue lights. Recently, active-matrix type organic EL panels provided with thin film transistors (TFTs) as switching elements are drawing much attention as a most promising next-generation flat panel display, and are therefore being developed at a high pitch.
Permeation of moisture compromises the reliability of organic EL elements; therefore, in manufacturing an organic EL panel, the outer surface of the organic EL elements is covered with a metal can or like encapsulation as a sealing structure capable of preventing the entry of moisture from outside. As another proposed arrangement, Japanese Patent Application Laid-Open No. Hei11-260562 discloses that an SiOx layer is formed between an organic layer and an organic EL layer as a structure that protects the organic EL layer from the entry of organic layer components or moisture.
In actuality, however, degradation of organic EL elements caused by moisture is a phenomenon often observed with organic EL panels which are provided with the sealing structure using the metal can or metal cap. As a result of analysis, inventors of the present invention had identified the cause of the problem as the moisture contained in the TFT substrate, which permeates the organic EL elements, thus compromising the reliability of the organic EL elements.
The SiOx layer that protects the organic EL layer against moisture, disclosed in the above published application, does not provide an excellent barrier against moisture. Furthermore, in forming the SiOx layer on the organic layer, the film must be formed at low temperatures to protect the organic layer, so that it is not possible to form a perfectly tight film capable of stopping the moisture from permeating the organic EL layer.